The invention relates to a semiconductor device comprising a semiconductor body with a semiconductor substrate on which a semiconductor layer structure of mutually substantially parallel semiconductor layers is provided, at the surface of which a mesa is formed which comprises only a portion, called first portion, of the semiconductor structure, while a portion of the semiconductor structure called second portion not forming part of the mesa is situated below and on either side of the mesa. The invention also relates to a method of manufacturing a semiconductor device of the kind mentioned above.
Such semiconductor devices are frequently used inter alia in optoelectronic devices in which the mesa forms part of, for example, a semiconductor diode laser, a radiation waveguide, or a photodiode, and which find their application in, for example, optical disc systems or bar code readers.
Such a semiconductor device is known from the article by M. C. Amann, "New Stripe-Geometry Laser with Simplified Fabrication Process" published in Electron. Lett. vol. 15, no. 14, Jul. 5, 1979, pp. 441-442. The known semiconductor device comprises a semiconductor diode laser of the so-called ridge waveguide type, in which a semiconductor layer structure is provided on an n-GaAs substrate, which structure has at its surface a strip-shaped mesa which comprises the first portion of the semiconductor layer structure, here a p-GaAs layer and part of a p-AlGaAs cladding layer, while the second portion of the semiconductor layer structure extending below and next to the mesa comprises an n-GaAs buffer layer, another n-AlGaAs cladding layer, a GaAs active layer, and the remaining part of the p-AlGaAs buffer layer. The upper and lower sides of the semiconductor device are provided with conductive layers. Such a semiconductor device has many advantages such as a simple manufacture, simple contacting, and low contact resistance.
A disadvantage of the known semiconductor device is that the mesa, which projects from the semiconductor body, is comparatively vulnerable, especially when one of its lateral dimensions is comparatively small, as is the case in a diode laser. Another disadvantage of the known semiconductor device is that unevennesses on the cleaving face, so-called cleavage steps, are formed in the vicinity of, often just below the mesa during cleaving of this semiconductor device, which is especially undesirable in an optoelectronic semiconductor device.